try now this code
<?php
$paged = ( get_query_var( 'paged' ) ) ? get_query_var( 'paged' ) : 1;
$title = get_term_by('slug', get_query_var('term'), get_query_var('taxonomy') );
$args = array(
'post_type' => 'suppliers',
'tax_query' => array(
array(
'taxonomy' => 'ad_category',
'field' => 'slug',
'terms' => array('basic_advertiser'),
),
array(
'taxonomy' => 'supplier_categories',
'field' => 'slug',
'terms' => $title->slug,
),
),
'paged' => $paged,
'orderby' => 'rand'
);
$the_query = new WP_Query( $args ); ?>
<?php if ($the_query->have_posts()) : while($the_query->have_posts()) : $the_query->the_post(); ?>
////////// Loop goes here /////////
<?php endwhile; ?>
<nav class="pagination">
<?php pagination_bar( $the_query ); ?>
</nav>
<?php wp_reset_postdata();
endif;
function wp_pagination($wp_query)
{
$big = 999999999;
echo paginate_links(array(
'base' => str_replace($big, '%#%', get_pagenum_link($big)),
'format' => '?paged=%#%',
'current' => max(1, get_query_var('paged')),
'total' => $wp_query->max_num_pages
));
}